Golf ball resin composition and golf ball

ABSTRACT

An object of the present invention is to provide a golf ball resin composition excellent in resilience. Another object of the present invention is to provide a golf ball excellent in a shot feeling and resilience. The golf ball resin composition of the present invention is characterized in that a storage modulus E′ (Pa) and a loss modulus E″ (Pa) satisfy a following expression;
 
log( E′/E″   2 )≧−6.08
 
when measured at the conditions of the temperature of 12° C., the oscillation frequency of 10 Hz, and a strain of 0.05% in a tensile mode using a dynamic viscoelasticity measuring apparatus.

FIELD OF THE INVENTION

The present invention relates to a golf ball resin composition and agolf ball using the same.

DESCRIPTION OF THE RELATED ART

As a golf ball construction, a one-piece golf ball comprising a golfball body, a two-piece golf ball comprising a core and a cover, athree-piece golf ball comprising a core consisting of a center and asingle-layered intermediate layer covering the center, and a covercovering the core, and a multi-piece golf ball comprising a coreconsisting of a center and at least two intermediate layers covering thecenter, and a cover covering the core are known. Ionomer resins are usedas materials constituting each layer of golf balls. Use of the ionomerresins as the constituent member of the golf ball provides the golf balltraveling a great distance, because of its high stiffness. Accordingly,ionomer resins are widely used as a material constituting a cover or anintermediate layer of the golf ball.

Japanese Patent Publication No. 2000-157646 A discloses a golf ballcover composition having a melt index (MI) of 1 dg/sec. or more andprimarily comprising a mixture of a base resin, blended with (d) a metalsoap obtained by neutralizing an organic acid having up to 29 carbonatoms with a monovalent to trivalent metal ion, in a mass ratio of thebase resin to the metal soap being 95:5 to 80:20, wherein the base resincomprises an ionomer resin component containing (a) a ternary ionomerresin consisting of a metal ion neutralized product of anolefin-unsaturated carboxylic acid-unsaturated carboxylate copolymerhaving an acid content of 12 wt % or less, and (b) a binary ionomerresin consisting of a metal ion neutralized product of anolefin-unsaturated carboxylic acid copolymer having an acid content of15 wt % or less in a ratio of 40:60 to 100:0; and (c) an unneutralizedrandom copolymer composed of olefin and unsaturated carboxylic acidmonomers, in a mass ratio of the ionomer resin component to (c) theunneutralized random copolymer being 75:25 to 100:0.

Japanese Patent Publication No. 2002-177417 A discloses a golf ballmaterial comprising a mixture which is essentially composed of 100 partsby mass of a base resin obtained by blending (a) an olefin-unsaturatedcarboxylic acid binary random copolymer and/or a metal ion-neutralizedolefin-unsaturated carboxylic acid binary random copolymer with (b) anolefin-unsaturated carboxylic acid-unsaturated carboxylate ternaryrandom copolymer and/or a metal ion neutralized olefin-unsaturatedcarboxylic acid-unsaturated carboxylate ternary random copolymer in amass ratio of 100:0 to 30:70; (c) 5 to 80 parts by mass of a fatty acidand/or fatty acid derivative having a molecular weight of 280 to 1,500;and (d) 0.1 to 10 parts by mass of a basic inorganic metal compoundcapable of neutralizing acidic groups left unneutralized in the baseresin and component (c).

Japanese Patent Publication No. 2002-219195 A discloses a golf ballmaterial comprising a mixture which is composed of essential components:100 parts by weight of a resinous component consisting of a base resinand (e) a non-ionomer thermoplastic elastomer, the base resin and theelastomer being blended in a weight ratio of 100:0 to 50:50; (c) 5 to 80parts by weight of a fatty acid and/or fatty acid derivative having amolecular weight of 280 to 1,500; and (d) 0.1 to 10 parts by weight of abasic inorganic metal compound capable of neutralizing acidic groupsleft unneutralized in the base resin and component (c), wherein the baseresin has (a) an olefin-unsaturated carboxylic acid binary randomcopolymer and/or a metal ion-neutralized olefin-unsaturated carboxylicacid binary random copolymer, blended with (b) an olefin-unsaturatedcarboxylic acid-unsaturated carboxylate ternary random copolymer and/ora metal ion neutralized olefin-unsaturated carboxylic acid-unsaturatedcarboxylate ternary random copolymer, in a weight ratio of 100:0 to25:75.

Japanese Patent Publication No. 2004-524418 A discloses a soft andresilient golf ball ethylene copolymer. The ethylene copolymer is athermoplastic composition comprising E/X/Y copolymers (where E isethylene, X is a C₃ to C₈ α,β ethylenically unsaturated carboxylic acid,and Y is a softening comonomer selected from alkyl acrylate and alkylmethacrylate wherein the alkyl groups have from 1-8 carbon atoms),wherein a. the E/X/Y copolymer has a melt index measured in accord withASTM D-1238, condition E, at 190° C. using a 2160 gram weight of atleast 75 grams per ten minutes, b. X is about 2-30 wt. % of the E/X/Ycopolymer and Y being about 17-40 wt. % of the E/X/Y copolymer, and c.at least 55% of X is neutralized by one or more alkali metal, transitionmetal, or an alkaline earth metal cations.

Japanese Patent Publication Nos. 2010-194313 and 2010-194315 disclose amulti-piece solid golf ball comprising a solid core encased by a coverof one or at least two layers, wherein the solid core has an inner corelayer and an outer core layer, wherein the inner core layer is formedprimarily of a resin composition obtained by mixing: 100 parts by massof a base resin consisting of (A-I) 30 mass % to 100 mass % of anolefin-unsaturated carboxylic acid-unsaturated carboxylic acid esterrandom terpolymer and/or a metal salt thereof and (A-II) 0 mass % to 70mass % of an olefin-unsaturated carboxylic acid random copolymer and/ora metal salt thereof, (B) 5 to 170 parts by mass of a fatty acid havinga molecular weight of from 280 to 1,500 or derivatives thereof, and (C)0.1 to 10 parts by mass of a basic inorganic metal compound capable ofneutralizing acid groups in components (A) and (B).

SUMMARY OF THE INVENTION

Cured products of rubber compositions have been used for cores of golfballs. However, the cured products of the rubber compositions have aproblem of not being recycled after molding the core since the curedproducts of the rubber compositions have no thermoplasticity. Althoughmolding cores from thermoplastic resins capable of injection molding hasbeen studied, a soft material with an excellent resilience like thecured product of the rubber composition has not been obtained.

The present invention has been achieved in view of the abovecircumstances. An object of the present invention is to provide a golfball resin composition capable of injection molding with an excellentresilience. Another object of the present invention is to provide a golfball with an excellent shot feeling and resilience.

The golf ball resin composition of the present invention ischaracterized in that a storage modulus E′ (Pa) and a loss modulus E″(Pa) satisfy a following expression;log(E′/E″ ²)≧−6.08when measured at the conditions of a temperature of 12° C., anoscillation frequency of 10 Hz, and a strain of 0.05% in a tensile modeusing a dynamic viscoelasticity measuring apparatus. It is thought thatthe resilience of the golf ball resin composition becomes higher as thestorage modulus E′ (Pa) becomes larger or as the loss modulus E″ (Pa)becomes smaller. In addition, hardness also increases as the storagemodulus E′ (Pa) becomes larger. In the above described expression, sincethe denominator is the second power of the loss modulus E″ whereas thenumerator is the first power of the storage modulus E′, the abovedescribed expression means that reducing the loss modulus E″ provides alarger improvement effect on the resilience than increasing the storagemodulus E′ to enhance the hardness. The golf ball resin composition hasbetter resilience when the storage modulus E′ (Pa) and the loss modulusE″ (Pa) satisfy the above formula. The golf ball having a constituentmember formed from such golf ball resin composition is excellent in shotfeeling and resilience.

The golf ball resin composition of the present invention satisfying theabove expression is not limited, as long as the golf ball resincomposition contains a resin component. The golf ball resin compositionpreferably includes (A) at least one resin component selected from thegroup consisting of (a-1) a binary copolymer composed of an olefin andan α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; (a-2) anionomer resin consisting of a metal ion-neutralized product of a binarycopolymer composed of an olefin and an α,β-unsaturated carboxylic acidhaving 3 to 8 carbon atoms; (a-3) a ternary copolymer composed of anolefin, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms,and an α,β-unsaturated carboxylic acid ester; and (a-4) an ionomer resinconsisting of a metal ion-neutralized product of a ternary copolymercomposed of an olefin, an α,β-unsaturated carboxylic acid having 3 to 8carbon atoms, and an α,β-unsaturated carboxylic acid ester. Further, thegolf ball resin composition preferably includes (B) a metal salt of afatty acid.

According to the present invention, the golf ball resin compositioncapable of injection molding with an excellent resilience is obtained.The golf ball using the golf ball resin composition of the presentinvention provides an excellent shot feeling and resilience.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing a relation between coefficient of Restitutionand log (E′/E″²).

DESCRIPTION OF THE PREFERRED EMBODIMENT

The golf ball resin composition of the present invention ischaracterized in that the storage modulus E′ (Pa) and the loss modulusE″ (Pa) satisfy a following expression;log(E′/E″ ²)≧−6.08when measured at the conditions of the temperature of 12° C., theoscillation frequency of 10 Hz, and a strain of 0.05% in a tensile modeusing a dynamic viscoelasticity measuring apparatus. The resilience ofthe golf ball resin composition increases when the storage modulus E′(Pa) and the loss modulus E″ (Pa) satisfy the expression. Log (E′/E″²)is more preferably −6.01 or more. Further, log (E′/E″²) is, but notlimited to, preferably −5.25 or less, more preferably −5.40 or less,because when the log(E′/E″²) is −5.25, the coefficient of Restitutionalmost reaches the maximum value of 1. Log (E′/E″²) is controlled bychoosing appropriately the kinds, contents, or the like of (A) resincomponent and (B) component. In addition, log in the above expression iscommon logarithm.

The storage modulus E′ (Pa) is preferably 1×10⁵ Pa or more, morepreferably 2×10⁵ Pa or more, and is preferably 50×10⁷ Pa or less, morepreferably 49×10⁷ Pa or less. If the storage modulus E′ (Pa) is 1×10⁵ Paor more, a shape of a golf ball is maintained. If the storage modulus E′(Pa) is 50×10⁷ Pa or less, the shot feeling becomes better. The lossmodulus E″ (Pa) is preferably 1×10³ Pa or more, more preferably 2×10³ Paor more, and is preferably 2.1×10⁷ Pa or less, more preferably 2.05×10⁷Pa or less. If the loss modulus E″ (Pa) is 1×10³ Pa or more, thedurability becomes better. If the loss modulus E″ (Pa) is 2.1×10⁷ Pa orless, the resilience becomes better.

The reasons of employing the measurement conditions of the oscillationfrequency: 10 Hz, the temperature: 12° C. as the conditions of measuringthe dynamic viscoelasticity are follows. The contact time between thegolf ball and a collision bar (cylindrical metallic material) is 500micro seconds in measuring coefficient of restitution at 40 m/s. If thisis considered as a deformation of one cycle, this deformationcorresponds to a deformation at the several thousands Hertz. Based onthe frequency and temperature superposition principle of the generalionomer resin, the dynamic viscoelasticity measured at the conditions oftemperature: room temperature and oscillation frequency: severalthousands Hertz corresponds to the dynamic viscoelasticity measured atthe conditions of temperature: 12° C. and oscillation frequency: 10 Hz.It is thought that the reason why the strain is 0.05% is that the straincan be expressed by a liner strain of 0.05% because the strain inmeasuring the coefficient of restitution is in the range of a linerstrain.

The golf ball resin composition of the present invention satisfying theabove expression is, for example, obtained by modifying (A) at least oneresin component selected from the group consisting of (a-1) the binarycopolymer composed of an olefin and an α,β-unsaturated carboxylic acidhaving 3 to 8 carbon atoms; (a-2) the ionomer resin consisting of ametal ion-neutralized product of a binary copolymer composed of anolefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbonatoms; (a-3) a ternary copolymer composed of an olefin, anα,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and anα,β-unsaturated carboxylic acid ester; and (a-4) an ionomer resinconsisting of a metal ion-neutralized product of a ternary copolymercomposed of an olefin, an α,β-unsaturated carboxylic acid having 3 to 8carbon atoms, and an α,β-unsaturated carboxylic acid ester in a desiredmanner. For example, the golf ball resin composition of the presentinvention is obtained by blending (B) the metal salt of the fatty acidinto (A) the resin component.

First, (A) at least one resin component selected from the groupconsisting of (a-1) the binary copolymer composed of an olefin and anα,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; (a-2) theionomer resin consisting of a metal ion-neutralized product of a binarycopolymer composed of an olefin and an α,β-unsaturated carboxylic acidhaving 3 to 8 carbon atoms; (a-3) the ternary copolymer composed of anolefin, an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms,and an α,β-unsaturated carboxylic acid ester; and (a-4) the ionomerresin consisting of a metal ion-neutralized product of a ternarycopolymer composed of an olefin, an α,β-unsaturated carboxylic acidhaving 3 to 8 carbon atoms, and an α,β-unsaturated carboxylic acid esterwill be explained.

(a-1) component is a nonionic binary copolymer composed of an olefin andan α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms whereinthe carboxyl groups thereof are not neutralized. Further, (a-2)component includes an ionomer resin prepared by neutralizing at least apart of carboxyl groups in the binary copolymer composed of an olefinand α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms with ametal ion.

(a-3) component is a nonionic ternary copolymer composed of an olefin,an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and anα,β-unsaturated carboxylic acid ester wherein the carboxyl groupsthereof are not neutralized. (a-4) component includes an ionomer resinprepared by neutralizing at least a part of carboxyl groups in theternary copolymer composed of an olefin and α,β-unsaturated carboxylicacid having 3 to 8 carbon atoms, and an α,β-unsaturated carboxylic acidester with a metal ion.

In the present invention, “(a-1) the binary copolymer composed of anolefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbonatoms” is sometimes merely referred to as “binary copolymer”. “(a-2) Theionomer resin consisting of a metal ion-neutralized product of a binarycopolymer composed of an olefin and an α,β-unsaturated carboxylic acidhaving 3 to 8 carbon atoms” is sometimes referred to as “the binaryionomer resin”. “(a-3) The ternary copolymer composed of an olefin, anα,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and anα,β-unsaturated carboxylic acid ester” is sometimes merely referred toas “ternary copolymer”. “(a-4) The ionomer resin consisting of a metalion-neutralized product of a ternary copolymer composed of an olefin, anα,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and anα,β-unsaturated carboxylic acid ester” is sometimes referred to as “theternary ionomer resin”.

The olefin preferably includes an olefin having 2 to 8 carbon atoms.Examples of the olefin, for example, are ethylene, propylene, butene,pentene, hexene, heptene, and octene. The olefin more preferablyincludes ethylene. Examples of the α,β-unsaturated carboxylic acidhaving 3 to 8 carbon atoms, for example, are acrylic acid, methacrylicacid, fumaric acid, maleic acid and crotonic acid. Among these, acrylicacid and methacrylic acid are particularly preferred. Examples of theα,β-unsaturated carboxylic acid ester include methyl ester, ethyl ester,propyl ester, n-butyl ester, isobutyl ester of acrylic acid, methacrylicacid, fumaric acid, maleic acid or the like. In particular, acrylic acidester and methacrylic acid ester are preferable.

(a-1) The binary copolymer preferably includes a binary copolymercomposed of ethylene and (meth)acrylic acid. (a-2) The binary ionomerresin preferably includes the metal ion-neutralized product of thebinary copolymer composed of ethylene-(meth)acrylic acid. (a-3) Theternary copolymer preferably includes a ternary copolymer composed ofethylene, (meth)acrylic acid, and (meth)acrylic acid ester. (a-4) Theternary ionomer resin preferably includes the metal ion-neutralizedproduct of the ternary copolymer composed of ethylene, (meth)acrylicacid, and (meth)acrylic acid ester. Here, (meth) acrylic acid meansacrylic acid and/or methacrylic acid.

The content of the α,β-unsaturated carboxylic acid component having 3 to8 carbon atoms in (a-1) the binary copolymer or (a-3) the ternarycopolymer is preferably 4 mass % or more, more preferably 5 mass % ormore, and is preferably 30 mass % or less, more preferably 25 mass % orless.

The melt flow rate (190° C., 2.16 kg) of (a-1) the binary copolymer or(a-3) the ternary copolymer is preferably 5 g/10 min or more, morepreferably 10 g/10 min or more, and even more preferably 15 g/10 min ormore, and is preferably 1,700 g/10 min or less, more preferably 1,500g/10 min or less, even more preferably 1,300 g/10 min or less. If themelt flow rate (190° C., 2.16 kg) of (a-1) the binary copolymer or (a-3)the ternary copolymer is 5 g/10 min or more, the golf ball resincomposition has better fluidity, and thus it is easier to mold aconstituent member. If the melt flow rate (190° C., 2.16 kg) of (a-1)the binary copolymer or (a-3) the ternary copolymer is 1,700 g/10 min orless, the resultant golf ball has better durability.

Specific examples of (a-1) the binary copolymer include anethylene-methacrylic acid copolymer such as “Nucrel (registeredtrademark) (e.g. NUCREL N1050H, NUCREL N2050H, NUCREL N1110H, NUCRELN0200H) manufactured by Du Pont-Mitsui Polychemicals Co, and anethylene-acrylic acid copolymer such as “Primacore (registeredtrademark) 5980I” available from Dow Chemical Company.

Specific examples of (a-3) the ternary copolymer include “Nucrel(registered trademark) (e.g. NUCREL AN4318, NUCREL AN4319) manufacturedby Du Pont-Mitsui Polychemicals Co, and “Nucrel (registered trademark)(e.g. NUCREL AE) manufactured by E.I. du Pont de Nemours and Company,and “Primacore (registered trademark) (e.g. PRIMCOR AT310, PRIMCORAT320) available from Dow Chemical Company. (a-1) The binary copolymeror (a-3) the ternary copolymer may be used alone or as a mixture of atleast two of them.

The content of the α,β-unsaturated carboxylic acid having 3 to 8 carbonatoms of (a-2) the binary ionomer resin is preferably 15 mass % or more,more preferably 16 mass % or more, and even more preferably 17 mass % ormore, and is preferably 30 mass % or less, more preferably 25 mass % orless. If the content of the α,β-unsaturated carboxylic acid having 3 to8 carbon atoms is 15 mass % or more, the resultant constituent memberhas a desirable hardness. If the content of the α,β-unsaturatedcarboxylic acid having 3 to 8 carbon atoms is 30 mass % or less, sincethe hardness of the resultant constituent member does not becomeexcessively high, the durability and shot feeling become better.

The degree of neutralization of the carboxyl groups contained in (a-2)the binary ionomer resin is preferably 15 mole % or more, morepreferably 20 mole % or more, and is preferably 90 mole % or less, morepreferably 85 mole % or less. If the degree of neutralization is 15 mole% or more, the resultant golf ball has better resilience and durability.On the other hand, If the degree of neutralization is 90 mole % or less,the golf ball resin composition has better fluidity (good moldability).The degree of neutralization of the carboxyl groups of (a-2) the binaryionomer resin can be calculated by the following expression.Degree of neutralization (mol %) of the binary ionomer resin=(the numberof moles of carboxyl groups neutralized in the binary ionomer resin/thenumber of moles of all carboxyl groups contained in the binary ionomerresin)×100

Examples of a metal ion used for neutralizing at least a part ofcarboxyl groups of (a-2) the binary ionomer resin include: monovalentmetal ions such as sodium, potassium, lithium, or the like; divalentmetals ions such as magnesium, calcium, zinc, barium, cadmium, or thelike; trivalent metals ions such as aluminum or the like; and othermetals ions such as tin, zirconium, or the like.

Specific examples of (a-2) the binary ionomer resin include trade name“Himilan (registered trademark) (e.g. Himilan 1555 (Na), Himilan 1557(Zn), Himilan 1605 (Na), Himilan 1706 (Zn), Himilan 1707 (Na), HimilanAM7311 (Mg), Himilan AM7329(Zn))” commercially available from DuPont-Mitsui Polychemicals Co., Ltd.

Further, examples include “Surlyn (registered trademark) (e.g. Surlyn8945 (Na), Surlyn 9945 (Zn), Surlyn 8140 (Na), Surlyn 8150 (Na), Surlyn9120 (Zn), Surlyn 9150 (Zn), Surlyn 6910 (Mg), Surlyn 6120 (Mg), Surlyn7930 (Li), Surlyn 7940 (Li), Surlyn AD8546 (Li))” commercially availablefrom E.I. du Pont de Nemours and Company.

Further, examples include “Iotek (registered trademark) (e.g. Iotek 8000(Na), Iotek 8030 (Na), Iotek 7010 (Zn), Iotek 7030 (Zn))” commerciallyavailable from ExxonMobil Chemical Corporation.

(a-2) The binary ionomer resins may be used alone or as a mixture of atleast two of them. It is noted that Na, Zn, Li, and Mg described in theparentheses after the trade names indicate metal types of neutralizingmetal ions of the binary ionomer resins.

(a-2) The binary ionomer resin preferably has a bending stiffness of 140MPa or more, more preferably 150 MPa or more, and even more preferably160 MPa or more, and preferably has a bending stiffness of 550 MPa orless, more preferably 500 MPa or less, even more preferably 450 MPa orless. If the bending stiffness of (a-2) the binary ionomer resin is toolow, the flight distance tends to be shorter because of the increasedspin rate of the golf ball. If the bending stiffness is too high, thedurability of the golf ball may be lowered.

(a-2) The binary ionomer resin preferably has the melt flow rate (190°C., 2.16 kg) of 0.1 g/10 min or more, more preferably 0.5 g/10 min ormore, and even more preferably 1.0 g/10 min or more, and preferably hasthe melt flow rate (190° C., 2.16 kg) of 30 g/10 min or less, morepreferably 20 g/10 min or less, and even more preferably 15 g/10 min orless. If the melt flow rate of (a-2) the binary ionomer resin is 0.1g/10 min or more, the golf ball resin composition has better fluidityand thus it is easy to mold the thin layer. If the melt flow rate of(a-2) the binary ionomer resin is 30 g/10 min or less, the durability ofthe resultant golf ball becomes better.

(a-2) The binary ionomer resin preferably has a slab hardness of 50 ormore, more preferably 55 or more, even more preferably 60 or more, andpreferably has a slab hardness of 75 or less, more preferably 73 orless, even more preferably 70 or less in Shore D hardness. If the binaryionomer resin has a slab hardness of 50 or more in Shore D hardness, theresultant constituent member has a high hardness. If the binary ionomerresin has a slab hardness of 75 or less in Shore D hardness, theresultant constituent member does not become excessively hard and thusthe obtained golf ball has better durability.

The content of the α,β-unsaturated carboxylic acid having 3 to 8 carbonatoms in (a-4) the ternary ionomer resin is preferably 2 mass % or more,more preferably 3 mass % or more, and is preferably 30 mass % or less,more preferably 25 mass % or less.

The degree of neutralization of the carboxyl groups contained in (a-4)the ternary ionomer resin is preferably 20 mole % or more, morepreferably 30 mole % or more, and is preferably 90 mole % or less, morepreferably 85 mole % or less. If the degree of neutralization is 20 mole% or more, the resultant golf ball obtained by using the golf ball resincomposition of the present invention has better resilience anddurability. If the degree of neutralization is 90 mole % or less, thegolf ball resin composition has better fluidity (good moldability). Thedegree of neutralization of the carboxyl groups in the ionomer resin canbe calculated by the following expression.Degree of neutralization (mol %) of the ionomer resin=(the number ofmoles of carboxyl groups neutralized in the ionomer resin/the number ofmoles of all carboxyl groups contained in the ionomer resin)×100

Examples of a metal ion used for neutralizing at least a part ofcarboxyl groups of (a-4) the ternary ionomer resin include: monovalentmetal ions such as sodium, potassium, lithium, or the like; divalentmetals ions such as magnesium, calcium, zinc, barium, cadmium, or thelike; trivalent metals ions such as aluminum or the like; and othermetals ions such as tin, zirconium, or the like.

Specific examples of (a-4) the ternary ionomer resin include trade name“Himilan (registered trademark) (e.g. Himilan AM7327 (Zn), Himilan 1855(Zn), Himilan 1856 (Na), Himilan AM7331 (Na), or the like)” commerciallyavailable from Du Pont-Mitsui Polychemicals Co., Ltd. Further, theternary ionomer resins commercially available from E.I. du Pont deNemours and Company include trade name “Surlyn (registered trademark)(e.g. Surlyn 6320 (Mg), Surlyn 8120 (Na), Surlyn 8320 (Na), Surlyn 9320(Zn), Surlyn 9320W (Zn) or the like)”. The ionomer resins commerciallyavailable from ExxonMobil Chemical Corporation include trade name “Iotek(registered trademark) (e.g. Iotek 7510 (Zn), Iotek 7520 (Zn) or thelike)”. It is noted that Na, Zn, Li, and Mg described in the parenthesesafter the trade names indicate metal types of neutralizing metal ions.(a-4) The ternary ionomer resins may be used alone or as a mixture of atleast two of them.

(a-4) The ternary ionomer resin preferably has a bending stiffness of 10MPa or more, more preferably 11 MPa or more, even more preferably 12 MPaor more, and preferably has a bending stiffness of 100 MPa or less, morepreferably 97 MPa or less, even more preferably 95 MPa or less. If thebending stiffness of (a-4) the ternary ionomer resin is too low, theflight distance tends to be shorter because of the increased spin rateof the golf ball. If the bending stiffness is too high, the durabilityof the golf ball may be lowered.

(a-4) The ternary ionomer resin preferably has the melt flow rate (190°C., 2.16 kg) of 0.1 g/10 min or more, more preferably 0.3 g/10 min ormore, and even more preferably 0.5 g/10 min or more, and preferably hasthe melt flow rate (190° C., 2.16 kg) of 20 g/10 min or less, morepreferably 15 g/10 min or less, even more preferably 10 g/10 min orless. If the melt flow rate (190° C., 2.16 kg) of (a-4) the ternaryionomer resin is 0.1 g/10 min or more, the golf ball resin compositionhas better fluidity and thus it is easy to mold a thin layer. If themelt flow rate (190° C., 2.16 kg) of (a-4) the ternary ionomer resin is20 g/10 min or less, the durability of the resultant golf ball becomesbetter.

(a-4) The ternary ionomer resin preferably has a slab hardness of 20 ormore, more preferably 25 or more, even more preferably 30 or more, andpreferably has a slab hardness of 70 or less, more preferably 65 orless, even more preferably 60 or less in Shore D hardness. If theternary ionomer resin has a slab hardness of 20 or more in Shore Dhardness, the resultant constituent member does not become excessivelysoft and thus the golf ball has higher resilience. If the ternaryionomer resin has a slab hardness of 70 or less in Shore D hardness, theresultant constituent member does not become excessively hard and thusthe golf ball has better durability.

As (A) the resin component, (a-1) the binary copolymer, (a-2) the binaryionomer resin, (a-3) the ternary copolymer, and (a-4) the ternaryionomer resin may be used alone or as a mixture of at least two of them.The golf ball resin composition of the present invention preferablyincludes (a-3) the ternary copolymer or (a-4) the ternary ionomer resinas (A) the resin component, because the resultant constituent memberdoes not become excessively hard, and thus the golf ball has higherresilience.

The golf ball resin composition of the present invention preferablycontains (A) the resin component and (B) the metal salt of the fattyacid. If the golf ball resin composition contains (B) the metal salt ofthe fatty acid, the unneutralized carboxyl groups of (A) the resincomponent are neutralized and thus the resilience improves. In thefollowings, (B) the metal salt of the fatty acid will be explained. (B)The metal salt of the fatty acid is not limited, as long as the metalsalt of the fatty acid is the metal salt of the aliphatic carboxylicacid. (B) The metal salt of the fatty acid may include any one of themetal salts of saturated fatty acids and the metal salts of theunsaturated fatty acids. (B) The metal salt of the fatty acid preferablyincludes the metal salt of the fatty acid having 18 to 30 carbon atoms,more preferably the metal salt of the fatty acid having 18 to 28 carbonatoms.

Specific examples the fatty acid component of (B) the metal salt of thefatty acid include stearic acid (C18), oleic acid (C18), linoleic acid(C18), linolenic acid (C18), 12-hydroxy stearic acid (C18), arachidicacid (C20), arachidonic acid (C20), behenic acid (C22), lignoceric acid(C24), nervonic acid (C24), cerotic acid (C26), montanic acid (C28), andmelissic acid (C30). The above fatty acid components may be used solelyor as a mixture of at least two of them. Among them, stearic acid,behenic acid or montanic acid is preferable as the fatty acid component.

Examples of metal components of (B) the metal salt of the fatty acidinclude: monovalent metal ions such as sodium, potassium, lithium, orthe like; divalent metal ions such as magnesium, calcium, zinc, barium,cadmium, or the like; trivalent metal ions such as aluminum or the like;and other metal ions such as tin, zirconium, or the like. The abovemetal components may be used solely or as a mixture of at least two ofthem. Among these metal components, preferred are the divalent metalssuch as magnesium, calcium, barium, or the like.

Specific examples of (B) the metal salt of the fatty acids are magnesiumstearate, calcium stearate, barium stearate, magnesium behenate, calciumbehenate, barium behenate, magnesium montanate, calcium montanate, orbarium montanate. (B) The metal salt of the fatty acids may be usedsolely or as a mixture of at least two of them.

The golf ball resin composition of the present invention preferablycontains (B) the metal salt of the fatty acid in an amount of 25 partsor more, more preferably 33 parts or more, even more preferably 50 partsor more, and preferably contains (B) the metal salt of the fatty acid inan amount of 100 parts or less, more preferably 98 parts or less, evenmore preferably 95 parts or less, even more preferably 90 parts or less,with respect to 100 parts of (A) the resin component by mass. If thecontent of (B) the metal salt of the fatty acid is 25 parts by mass ormore, the resilience of the golf ball improves, while if the content is100 parts by mass or less, it is possible to suppress the lowering ofthe durability of the golf ball due to the increase in the low molecularweight component.

The golf ball resin composition of the present invention preferablycontains only (A) the resin component as the resin component. However,the golf ball resin composition may contain a thermoplastic elastomerand a thermoplastic resin, as long as they do not impair the effect ofthe present invention.

Examples of other thermoplastic elastomers are a thermoplastic polyamideelastomer having a commercial name of “Pebax (e.g. “Pebax 2533”)”commercially available from Arkema K. K.; a thermoplastic polyurethaneelastomer having a commercial name of “Elastollan (e.g. “ElastollanXNY85A”)” commercially available from BASF Japan Ltd; a thermoplasticpolyester elastomer having a commercial name of “Hytrel (e.g. “Hytrel3548”, “Hytrel 4047”)” commercially available from Du Pont-Toray Co.,Ltd.; a thermoplastic polystyrene elastomer having a commercial name of“Rabalon (e.g. “Rabalon T3221C”)” commercially available from MitsubishiChemical Corporation; and the like.

In the present invention, the golf ball resin composition may furthercontain a pigment component such as a white pigment (for example,titanium oxide) and a blue pigment, a weight adjusting agent, adispersant, an antioxidant, an ultraviolet absorber, a light stabilizer,a fluorescent material, a fluorescent brightener, and the like, as longas they do not impair the effect of the present invention.

The content of the white pigment (for example, titanium oxide) ispreferably 0.5 part or more, more preferably 1 part or more, and thecontent of the white pigment is preferably 10 parts or less, morepreferably 8 parts or less, with respect to 100 parts of the resincomponent by mass. If the amount of the white pigment is 0.5 part bymass or more, it is possible to impart the opacity to the resultant golfball constituent member. Further, if the amount of the white pigment ismore than 10 parts by mass, the durability of the resultant golf ballmay deteriorate.

The golf ball resin composition of the present invention can beobtained, for example, by dry blending the (A) component and the (B)component. Further, the golf ball resin composition of the presentinvention can be obtained by extruding the dry blended mixture in theform of pellet. The dry blending may be carried out using for example, amixer capable of blending a raw material in the form of pellet, morepreferably a tumbler type mixer. Extruding can be carried out bypublicly known extruders such as a single-screw kneading extruder, atwin-screw kneading extruder, and a twin-single kneading extruder.

The golf ball resin composition of the present invention preferably hasa hardness of 20 or larger, more preferably 25 or larger, and even morepreferably 30 or larger in shore D hardness, and the golf ball resincomposition preferably has a hardness of 65 or smaller, more preferably60 or smaller, and even preferably 56 or smaller in shore D hardness.Use of the golf ball resin composition having a hardness of 20 or largerin shore D hardness provides the golf ball excellent in the resilience(flying distance). On the other hand, use of the golf ball resincomposition having a hardness of 65 or smaller in shore D hardnessprovides the golf ball excellent in the shot feeling. Here, a hardnessof the golf ball resin composition is a slab hardness of the golf ballresin composition that is molded into a sheet form. The method for themeasurement is described later.

The golf ball resin composition of the present invention preferably hasthe melt flow rate (190° C., 2.16 kg) of 0.01 g/10 min or more, morepreferably 0.05 g/10 min or more, and even more preferably 0.1/10 min ormore, and preferably has 100 g/10 min or less, more preferably 80 g/10min or less, and even more preferably 50 g/10 min or less. If the golfball resin composition has the melt flow rate in the above range, themoldability into the golf ball constituent member is good.

The golf ball resin composition preferably has a bending stiffness of 10MPa or more, more preferably 15 MPa or more, even more preferably 20 MPaor more, and preferably has a bending stiffness of 450 MPa or less, morepreferably 400 MPa or less, even more preferably 350 MPa or less. Use ofthe golf ball resin composition having a bending stiffness of 10 MPa ormore provides the golf ball excellent in the resilience (flyingdistance). On the other hand, if the bending stiffness is 450 MPa orless, the obtained golf ball becomes appropriately soft and thus theshot feeling becomes good.

The golf ball resin composition of the present invention preferably hasa rebound resilience of 40% or more, more preferably 43% or more, evenmore preferably 46% or more. Use of the golf ball resin compositionhaving a rebound resilience of 40% or more provides the golf ballexcellent in the resilience (flying distance). Here, the bendingstiffness and the rebound resilience of the golf ball resin compositionare measured by molding the golf ball resin composition into a sheetform. The methods for the measurement are described later.

The golf ball of the present invention is not limited, as long as itcomprises a constituent member formed from the golf ball resincomposition of the present invention. For example, in a one-piece golfball, in a two-piece golf ball comprising a single-layered core and acover disposed around the core, in a three-piece golf ball comprising acore having a center and a single-layered intermediate layer disposedaround the center, and a cover disposed around the core, and in amulti-piece golf ball comprising a core having a center and at least oneintermediate layer disposed around the center, and a cover disposedaround the core (including the three-piece golf ball mentioned above),anyone of constituent members is formed from the above golf ball resincomposition. In one preferable embodiment, the golf ball comprises acore composed of at least one layer and a cover disposed around thecore, wherein at least one layer of the core is formed from the golfball resin composition of the present invention. In another preferableembodiment, the golf ball body of the one-piece golf ball is formed fromthe golf ball resin composition of the present invention. In particular,in one more preferable embodiment, the two-piece golf ball comprises asingle-layered core and a cover disposed around the core, wherein thesingle-layered core is formed from the golf ball resin composition ofthe present invention. Also, in another more preferable embodiment, themulti-piece golf ball comprises a core having a center and at least oneintermediate layer disposed around the center, and a cover disposedaround the core, wherein the center is formed from the golf ball resincomposition of the present invention.

In the following, the present invention will be explained based on thetwo-piece golf ball that comprises a core and a cover disposed aroundthe core, wherein the core is formed from the golf ball resincomposition of the present invention. However, the present invention isnot limited to this embodiment.

The core, for example, is molded by injection molding the golf ballresin composition of the present invention. Specifically, it ispreferred that the golf ball resin composition heated and melted at thetemperature ranging from 160° C. to 260° C. is charged into a mold heldunder the pressure of 1 MPa to 100 MPa for 1 second to 100 seconds, andafter cooling for 30 seconds to 300 seconds, the mold is opened.

The core preferably has a spherical shape. If the core does not have aspherical shape, the cover does not have a uniform thickness. As aresult, there exist some portions where the performance of the cover islowered.

The core preferably has the diameter of the 39.00 mm or more, morepreferably 39.25 mm or more, and even more preferably 39.50 mm or more,and preferably has the diameter of 42.37 mm or less, more preferably42.22 mm or less, and even more preferably 42.07 mm or less. If the corehas the diameter of 39.00 mm or more, the thickness of the cover doesnot become too thick and thus the resilience becomes better. On theother hand, if the core has the diameter of 42.37 mm or less, thethickness of the cover does not become too thin, and hence a protectionability of the cover is sufficiently provided.

When the core has a diameter from 39.00 mm to 42.37 mm, a compressiondeformation amount (shrinking deformation amount of the core along thecompression direction) of the core when applying a load from 98 N as aninitial load to 1275 N as a final load is preferably 1.00 mm or more,more preferably 1.10 mm or more, and is preferably 5.00 mm or less, morepreferably 4.90 mm or less, even more preferably 4.80 mm or less. If thecompression deformation amount is 1.00 mm or more, the shot feeling ofthe golf ball becomes better. If the compression deformation amount is5.00 mm or less, the resilience of the golf ball becomes better.

The surface hardness of the core is 20 or larger, more preferably 25 orlarger, and even more preferably 30 or larger in shore D hardness, andis preferably 70 or smaller, more preferably 69 or smaller in shore Dhardness. If the surface hardness is 20 or larger in shore D hardness,the core does not become so soft and the better resilience of the golfball is obtained. If the surface hardness of the core is 70 or smallerin shore D hardness, the core does not become so hard and the bettershot feeling is obtained.

The center hardness of the core is preferably 20 or larger, morepreferably 22 or larger, and even more preferably 24 or larger in ShoreD hardness. If the center hardness is less than 20 in shore D hardness,the core becomes so soft that the resilience of the golf ball tends tobecome lower. Further, the center hardness of the core is preferably 50or smaller, more preferably 48 or smaller, and even more preferably 46or smaller in Shore D hardness. If the center hardness is more than 50in shore D hardness, the core becomes too hard, resulting in the poorshot feeling. In the present invention, the center hardness of the coreis the hardness measured with the Shore D type spring hardness tester atthe central point of a cut plane of a core which has been cut into twohalves.

The core preferably contains a filler. The filler is mainly blended as aweight adjusting agent in order to adjust density of the golf ball asthe final product within the range of 1.0 to 1.5 g/cm³, and may beblended as required. Examples of the filler include an inorganic fillersuch as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide,tungsten powder, and molybdenum powder. The amount of the filler to beblended in the resin composition is preferably 0.5 part or more, morepreferably 1.0 part or more, and is preferably 30 parts or less, morepreferably 20 parts or less based on 100 parts of the resin component bymass. If the amount of the filler to be blended is less than 0.5 part bymass, it becomes difficult to adjust the weight, while if it is morethan 30 parts by mass, the weight ratio of the resin component becomessmall and the resilience tends to be lowered.

The cover of the golf ball of the present invention is preferably formedfrom a cover composition containing a resin component. The resincomponent includes, for example, various resins such as an ionomerresin, polyester resin, urethane resins such as a thermoplastic urethaneresin or two-component curable urethane resin, polyamide resin or thelike; and a thermoplastic polyamide elastomer having a commercial nameof “Pebax (registered trademark) (e.g. “Pebax 2533”)” commerciallyavailable from Arkema K. K.; a thermoplastic polyester elastomer havinga commercial name of “Hytrel (registered trademark) (e.g. “Hytrel 3548”,“Hytrel 4047”)” commercially available from Du Pont-Toray Co., Ltd.; athermoplastic polyurethane elastomer having a commercial name of“Elastollan (registered trademark) (e.g. “Elastollan XNY97A”)”commercially available from BASF Japan Ltd.; a thermoplastic polystyreneelastomer having a commercial name of “Rabalon (registered trademark)”commercially available from Mitsubishi Chemical Corporation. These resincomponents are used solely or as a mixture of at least two of them.

The ionomer resin preferably includes the resins exemplified as (a-2) or(a-4) components.

The cover composition preferably contains the polyurethane resin(including polyurethane elastomer) or the ionomer resin, as the resincomponent. The content of the polyurethane resin or the ionomer resin inthe resin component of the cover composition is preferably 50 mass % ormore, more preferably 60 mass % or more, even more preferably 70 mass %or more.

In the present invention, in addition to the aforementioned resincomponent, the cover composition may further contain a pigment componentsuch as a white pigment (for example, titanium oxide), a blue pigment, ared pigment, or the like; a weight adjusting agent such as zinc oxide,calcium carbonate, barium sulfate, or the like; a dispersant; anantioxidant; an ultraviolet absorber; a light stabilizer; a fluorescentmaterial; a fluorescent brightener; or the like, as long as they do notimpair the performance of the cover.

The amount of the white pigment (for example, titanium oxide), withrespect to 100 parts by mass of the resin component constituting thecover, is preferably 0.5 part by mass or more, more preferably 1 part bymass or more, and is preferably 10 parts by mass or less, morepreferably 8 parts by mass or less. If the amount of the white pigmentis 0.5 part by mass or more, it is possible to impart the opacity to thecover. If the amount of the white pigment is more than 10 parts by mass,the durability of the resultant cover may deteriorate.

An embodiment for molding a cover is not particularly limited, andincludes an embodiment which comprises injection molding the covercomposition directly onto the core, or an embodiment which comprisesmolding the cover composition into a hollow-shell, covering the corewith a plurality of the hollow-shells and subjecting the core with aplurality of the hollow shells to the compression-molding (preferably anembodiment which comprises molding the cover composition into a halfhollow-shell, covering the core with the two half hollow-shells, andsubjecting the core with the two half hollow-shells to thecompression-molding).

In the case of directly injection molding the cover composition, thecover composition extruded in the pellet form beforehand may be used forinjection molding or the materials such as the resin components and thepigment may be dry blended, followed by directly injection molding theblended material. It is preferred to use upper and lower molds forforming a cover having a spherical cavity and pimples, wherein a part ofthe pimples also serves as a retractable hold pin. When molding thecover by injection molding, the hold pin is protruded to hold the core,and the cover composition which has been heated and melted is chargedand then cooled to obtain a cover. For example, it is preferred that thecover composition heated and melted at the temperature ranging from 200°C. to 250° C. is charged into a mold held under the pressure of 9 MPa to15 MPa for 0.5 to 5 seconds, and after cooling for 10 to 60 seconds, themold is opened and the golf ball with the cover molded is taken out fromthe mold.

When molding a cover, the concave portions called “dimple” are usuallyformed on the surface. The total number of the dimples is preferably 200or more and 500 or less. If the total number is less than 200, thedimple effect is hardly obtained. On the other hand, if the total numberexceeds 500, the dimple effect is hardly obtained because the size ofthe respective dimples is small. The shape (shape in a plan view) ofdimples includes, for example, without limitation, a circle, polygonalshapes such as roughly triangular shape, roughly quadrangular shape,roughly pentagonal shape, roughly hexagonal shape, and another irregularshape. The shape of the dimples is employed solely or in combination atleast two of them.

In the present invention, the thickness of the cover of the golf ball ispreferably 2.0 mm or less, more preferably 1.6 mm or less, even morepreferably 1.2 mm or less, most preferably 1.0 mm or less. If thethickness of the cover is 2.0 mm or less, the resilience and shotfeeling of the obtained golf ball become better. The thickness of thecover is preferably 0.1 mm or more, more preferably 0.2 mm or more, andeven more preferably 0.3 mm or more. If the thickness of the cover isless than 0.1 mm, it may become difficult to mold the cover. Inaddition, the durability and the wear resistance of the cover maydeteriorate.

After the cover is molded, the mold is opened and the golf ball body istaken out from the mold, and as necessary, the golf ball body ispreferably subjected to surface treatments such as deburring, cleaning,and sandblast. If desired, a paint film or a mark may be formed. Thepaint film preferably has a thickness of, but not limited to, 5 μm orlarger, and more preferably 7 μm or larger, and preferably has athickness of 25 μm or smaller, and more preferably 18 μm or smaller. Ifthe thickness is smaller than 5 μm, the paint film is easy to wear offdue to continued use of the golf ball, and if the thickness is largerthan 25 μm, the effect of the dimples is reduced, resulting in loweringflying performance of the golf ball.

When the golf ball of the present invention has a diameter in a rangefrom 40 mm to 45 mm, a compression deformation amount of the golf ball(shrinking amount of the golf ball in the compression direction thereof)when applying an initial load of 98 N to a final load of 1275 N to thegolf ball is preferably 2.0 mm or more, more preferably 2.2 mm or more,and is preferably 4.0 mm or less, more preferably 3.5 mm or less. If thecompression deformation amount is 2.0 mm or more, the golf ball does notbecome excessively hard, and thus exhibits the good shot feeling. On theother hand, if the compression deformation amount is 4.0 mm or less, theresilience is enhanced.

The present invention is explained based on the embodiment where thegolf ball resin composition of the present invention is used for thecore, but the golf ball resin composition of the present invention maybe used as the center, the intermediate layers, and the cover. If thecenter is formed from the golf ball resin composition of the presentinvention, the intermediate layers may be formed from the resincomponents exemplified as the cover materials.

EXAMPLES

Hereinafter, the present invention will be described in detail by way ofexample. The present invention is not limited to examples describedbelow. Various changes and modifications can be made without departingfrom the spirit and scope of the present invention.

[Evaluation Methods]

(1) Slab Hardness (Shore D Hardness)

Sheets with a thickness of about 2 mm were produced by hot press moldingthe golf ball resin composition, and stored at 23° C. for two weeks.Three or more of these sheets were stacked on one another so as not tobe affected by the measuring substrate on which the sheets were placed,and the hardness of the stack was measured with a type P1 auto loadingdurometer manufactured by Kobunshi Keiki Co., Ltd., provided with aShore D type spring hardness tester prescribed in ASTM-D2240.

(2) Melt Flow Rate (MFR) (g/10 min)

The MFR was measured using a flow tester (Shimadzu flow tester CFT-100Cmanufactured by Shimadzu Corporation) in accordance with JIS K7210. Themeasurement was conducted under the conditions of the measurementtemperature 190° C. and the load of 2.16 kg.

(3) Rebound Resilience (%)

A sheet with a thickness of about 2 mm was produced by a hot pressmolding the golf ball resin composition. A circle-shaped test piecehaving a diameter of 28 mm was cut out of this sheet, and 6 pieces ofthe test piece were stacked to prepare a cylindrical test piece having athickness of about 12 mm and a diameter of 28 mm. The cylindrical testpiece was subjected to the Lupke type rebound resilience test (testingtemperature 23° C., humidity 50RH %). Preparation of the test piece andthe testing method are based on JIS K6255.

(4) Compression Deformation Amount (mm)

A compression deformation amount of the spherical body (a shrinkingamount of the spherical body in the compression direction thereof), whenapplying a load from 98 N as an initial load to 1275 N as a final loadto the spherical body, was measured. The compression deformation amountof spherical body No. 11 was defined as an index of 1.00, and thecompression deformation amounts of the other spherical bodies wererepresented by converting the compression deformation amounts of thespherical bodies into this index.

(5) Coefficient of Restitution

A 198.4 g of metal cylindrical object was forced to collide with eachspherical body at a speed of 40 m/sec, and the speeds of the cylindricalobject and the spherical body before and after the collision weremeasured. Based on these speeds and the mass of each object, coefficientof restitution for each spherical body was calculated. The measurementwas conducted by using twelve spherical bodies for each spherical body,and the average value was regarded as the coefficient of restitution forthe spherical body.

(6) Shot Feeling

An actual hitting test was carried out by ten amateur golfers (highskilled person) using a driver. Feeling at the shot was evaluated byeach person according to the following criteria. Major result of theevaluations of ten golfers was employed as the result of the golf ball.

E (Excellent): Impact is small and feeling is good.

G (Good): Normal feeling.

P (Poor): Impact is large and feeling is poor.

(7) Measurement of Storage Modulus E′ (Pa) and Loss Modulus E″ (Pa)

The storage modulus E′ (Pa) and the loss modulus E″ (Pa) of the golfball resin composition were measured at the following conditions.

-   Apparatus: Viscoelasticity measuring apparatus Rheogel-E4000    available from UBM CO., Ltd.-   Test piece: A sheet having a thickness of 2 mm was produced by a hot    press molding the golf ball resin composition and a test piece was    cut out to have a width 4 mm and a length between the clamps of 20    mm.-   Measuring mode: tensile mode-   Measuring temp.: 12° C.-   Oscillation frequency: 10 Hz-   Measuring strain: 0.05%    [Production of the Spherical Body (Core)]

As shown in Tables 1 and 2, the blending materials were dry blended,followed by mixing with a twin-screw kneading extruder to extrude theblended material in the strand form into the chilled water. The extrudedstrand was cut with a pelletizer to prepare a golf ball resincomposition in the form of pellet. Extrusion was performed in thefollowing conditions: screw diameter=45 mm; screw revolutions=200 rpm;and screw L/D=35. The mixtures were heated to a temperature in a rangefrom 160° C. to 230° C. at a die position of the extruder. The obtainedgolf ball resin composition in the form of pellet was injection moldedat a temperature of 220° C. to prepare a spherical body (core) having adiameter of 40 mm.

TABLE 1 Spherical body No. 1 2 3 4 5 6 7 8 9 10 Golf ball resin NUCRELAN4319 — — — — — — — 100 100 100 composition NUCREL N1560 — — — — — — —— — — Surlyn 6320 100 100 100 100 100 100 100 — — — Magnesium behenate25.7 33.1 70.2 89.8 99.8 20 120 — — — Behenic acid — — — — — — — — —Magnesium hydrate — — — — — — — 0.54 1.08 1.63 Properties Melt flow rate(g/10 min) 2.93 7.06 15.37 14.23 22 or 1.32 22 or 22 or 22 or 8.95 moremore more more Shore D hardness 49 53 54 55 56 46 58 34 37 40 Reboundresilience (%) 58 60 61 62 63 50 51 42 47 50 E′ (×10⁷ Pa) 32.4 41.5 44.046.7 49.4 26.5 55.3 7.86 8.15 11.0 E″ (×10⁷ Pa) 1.97 2.07 2.03 1.99 1.992.40 3.44 1.82 1.46 1.57 Log (E′/E″²) −6.08 −6.01 −5.97 −5.93 −5.90−6.34 −6.33 −6.62 −6.42 −6.35 Compression deformation 1.23 1.02 0.970.93 0.89 1.44 0.82 3.37 2.77 2.22 amount Coefficient of Restitution0.749 0.768 0.781 0.794 0.801 0.669 0.672 0.501 0.594 0.638 Shot feelingE E E E E E G E E E Formulation: parts by mass

TABLE 2 Spherical body No. 11 12 13 14 15 16 17 Golf ball resin NUCRELAN4319 — — — 100 100 100 100 composition NUCREL N1560 100 100 100 — — —— Surlyn 6320 — — — — — — — Magnesium behenate — — — — 20.61 41.21 61.82Behenic acid — — — 68.11 48.16 28.21 8.26 Magnesium hydrate — 2.03 3.05— — — — Properties Melt flow rate (g/10 min) 22 or 7.19 3.40 22 or 22 or22 or 22 or more more more more more Shore D hardness 53 63 63 44 47 4547 Rebound resilience (%) 37 55 56 26 30 31 33 E′ (×10⁷ Pa) 71.2 63.555.0 53.9 64.2 60.0 57.3 E″ (×10⁷ Pa) 7.75 3.07 2.79 8.62 8.21 7.67 6.84Log (E′/E″²) −6.93 −6.17 −6.15 −7.14 −7.02 −6.99 −6.91 Compressiondeformation 1.00 0.71 0.79 1.44 1.26 1.39 1.08 Amount Coefficient ofRestitution 0.554 0.755 0.752 0.414 0.453 0.491 0.549 Shot feeling E P PE E E E Formulation: parts by massThe materials used in Tables 1 and 2 are follows.

-   “Surlyn 6320”: a magnesium ion neutralized ethylene-methacrylic    acid-butyl acrylate ternary copolymer ionomer resin (melt flow rate    (190° C., 2.16 kg): 1.0 g/10 min) available from E.I. du Pont de    Nemours and Company-   “NUCREL AN 4319”: an ethylene-methacrylic acid-butyl acrylate    ternary copolymer (melt flow rate 190° C., 2.16 kg): 55 g/10 min,    bending stiffness: 21 PMa) available from Du Pont-Mitsui    Polychemicals Co., Ltd.-   “NUCREL N1560”: an ethylene-methacrylic acid copolymer (melt flow    rate (190° C., 2.16 kg): 60 g/10 min, shore D hardness: 53, bending    stiffness: 83 PMa) available from Du Pont-Mitsui Polychemicals Co.,    Ltd.-   Magnesium Behenate: Wako Pure Chemical Industries, Ltd.-   Behenic Acid: NOF Corporation-   Magnesium Hydroxide: Wako Pure Chemical Industries, Ltd.

As is apparent from Tables 1 and 2, the resilience of the golf ballresin composition is enhanced, in the case that the golf ball resincomposition is characterized in that a storage modulus E′ (Pa) and aloss modulus E″ (Pa) satisfy a following expression;log(E′/E″ ²)≧−6.08when measured at the conditions of the temperature of 12° C., theoscillation frequency of 10 Hz, and a strain of 0.05% in a tensile modeusing a dynamic viscoelasticity measuring apparatus.

FIG. 1 is a graph showing a correlation between the coefficient ofrestitution and log (E′/E″²). The result indicated that the coefficientof restitution increased as log (E′/E″²) becomes larger. In particular,it is note that if log (E′/E″²) was −6.08 or more, the core having thecoefficient of restitution of 0.749 or more was obtained.

According to the present invention, the golf ball with the excellentresilience and shot feeling is obtained. This application is based onJapanese Patent application No. 2010-293297 filed on Dec. 28, 2010, thecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A golf ball resin composition characterized inthat a storage modulus E′ (Pa) and a loss modulus E″ (Pa) satisfy afollowing expression;log (E′/E″ ²)≧−6.08 when measured at the conditions of a temperature of12° C., an oscillation frequency of 10 Hz, and a strain of 0.05% in atensile mode using a dynamic viscoelasticity measuring apparatus, andthe golf ball resin composition comprises: (A) at least one resincomponent selected from the group consisting of (a-1) a binary copolymercomposed of an olefin and an α,β-unsaturated carboxylic acid having 3 to8 carbon atoms; (a-2) an ionomer resin consisting of a metalion-neutralized product of a binary copolymer composed of an olefin andan α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; (a-3) aternary copolymer composed of an olefin, an α,β-unsaturated carboxylicacid having 3 to 8 carbon atoms, and an α,β-unsaturated carboxylic acidester; and (a-4) an ionomer resin consisting of a metal ion-neutralizedproduct of a ternary copolymer composed of an olefin, an α,β-unsaturatedcarboxylic acid having 3 to 8 carbon atoms, and an α,β-unsaturatedcarboxylic acid ester; and (B) a metal salt of a fatty acid in an amountranging from 25 parts to 100 parts by mass, with respect to 100 parts bymass of (A) the resin component.
 2. The golf ball resin compositionaccording to claim 1, wherein the metal salt of the fatty acid is ametal salt of a fatty acid having 18 to 30 carbon atoms.
 3. The golfball resin composition according to claim 1, wherein the fatty acidcomponent of the metal salt of the fatty acid includes stearic acid,behenic acid, or montanic acid.
 4. The golf ball resin compositionaccording to claim 1, wherein the metal component of the metal salt ofthe fatty acid includes magnesium, calcium, or barium.
 5. The golf ballresin composition according to claim 1, wherein the (A) resin componentcomprises (a-3) the ternary copolymer composed of the olefin, theα,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, and theα,β-unsaturated carboxylic acid ester, or (a-4) the ionomer resinconsisting of the metal ion-neutralized product of the ternary copolymercomposed of the olefin, the α,β-unsaturated carboxylic acid having 3 to8 carbon atoms, and the α,β-unsaturated carboxylic acid ester.
 6. Thegolf ball resin composition according to claim 1, wherein the golf ballresin composition has a hardness ranging from 20 to 65 in Shore Dhardness.
 7. The golf ball resin composition according to claim 1,wherein the golf ball resin composition has rebound resilience of 46% ormore.
 8. A golf ball comprising a core composed of at least one layerand a cover covering the core, wherein at least one layer of the core isformed from a golf ball resin composition characterized in that astorage modulus E′ (Pa) and a loss modulus E″ (Pa) satisfy a followingexpression;log (E′/E″ ²)≧−6.08 when measured at the conditions of a temperature of12° C., an oscillation frequency of 10 Hz, and a strain of 0.05% in atensile mode using a dynamic viscoelasticity measuring apparatus, andthe golf ball resin composition comprises: (A) at least one resincomponent selected from the group consisting of (a-1) a binary copolymercomposed of an olefin and an α,β-unsaturated carboxylic acid having 3 to8 carbon atoms; (a-2) an ionomer resin consisting of a metalion-neutralized product of a binary copolymer composed of an olefin andan α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; (a-3) aternary copolymer composed of an olefin, an α,β-unsaturated carboxylicacid having 3 to 8 carbon atoms, and an α,β-unsaturated carboxylic acidester; and (a-4) an ionomer resin consisting of a metal ion-neutralizedproduct of a ternary copolymer composed of an olefin, an α,β-unsaturatedcarboxylic acid having 3 to 8 carbon atoms, and an α,β-unsaturatedcarboxylic acid ester; and (B) a metal salt of a fatty acid in an amountranging from 25 parts to 100 parts by mass, with respect to 100 parts bymass of (A) the resin component.
 9. The golf ball according to claim 8,wherein the metal salt of the fatty acid is a metal salt of a fatty acidhaving 18 to 30 carbon atoms.
 10. The golf ball according to claim 8,wherein the fatty acid component of the metal salt of the fatty acidincludes stearic acid, behenic acid, or montanic acid.
 11. The golf ballaccording to claim 8, wherein the metal component of the metal salt ofthe fatty acid includes magnesium, calcium, or barium.
 12. The golf ballaccording to claim 8, wherein the (A) resin component comprises (a-3)the ternary copolymer composed of the olefin, the α,β-unsaturatedcarboxylic acid having 3 to 8 carbon atoms, and the α,β-unsaturatedcarboxylic acid ester, or (a-4) the ionomer resin consisting of themetal ion-neutralized product of the ternary copolymer composed of theolefin, the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms,and the α,β-unsaturated carboxylic acid ester.
 13. A one-piece golf ballcomprising a golf ball body formed from a golf ball resin compositioncharacterized in that a storage modulus E′ (Pa) and a loss modulus E″(Pa) satisfy a following expression;log (E′/E″ ²)≧−6.08 when measured at the conditions of a temperature of12° C., an oscillation frequency of 10 Hz, and a strain of 0.05% in atensile mode using a dynamic viscoelasticity measuring apparatus, andthe golf ball resin composition comprises: (A) at least one resincomponent selected from the group consisting of (a-1) a binary copolymercomposed of an olefin and an α,β-unsaturated carboxylic acid having 3 to8 carbon atoms; (a-2) an ionomer resin consisting of a metalion-neutralized product of a binary copolymer composed of an olefin andan α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; (a-3) aternary copolymer composed of an olefin, an α,β-unsaturated carboxylicacid having 3 to 8 carbon atoms, and an α,β-unsaturated carboxylic acidester; and (a-4) an ionomer resin consisting of a metal ion-neutralizedproduct of a ternary copolymer composed of an olefin, an α,β-unsaturatedcarboxylic acid having 3 to 8 carbon atoms, and an α,β-unsaturatedcarboxylic acid ester; and (B) a metal salt of a fatty acid in an amountranging from 25 parts to 100 parts by mass, with respect to 100 parts bymass of (A) the resin component.
 14. The one-piece golf ball accordingto claim 13, wherein the metal salt of the fatty acid is a magnesiumsalt, calcium salt, or barium salt of a fatty acid having 18 to 30carbon atoms.